David Dean PhD, Associate Professor, The Ohio State University
Additive manufacturing (3D Printing) has been used to produce metallic medical devices, including custom skeletal fixation devices. The majority of these 3D-printed devices are fabricated in Surgical Grade 5 Titanium (Ti-6Al-4V). With a high modulus of elasticity of 112 GPa relative to bone (i.e., 10-32 GPa), this hardware may fail due to this stiffness mismatch. Nitinol (NiTi) is less than half as stiff as Ti-6Al-4V. Printing nitinol with porosity can further reduce its stiffness. Moreover, in regards to bone fixation, nitinol has the desirable property of superelasticity. A stiffness matching approach using nitinol can minimize the risk of bone resorption due to stress shielding as well as stress concentration within the fixation device which can lead to loosening or fracture of the device. Newly completed work done with the University of Toledo and the University of Kentucky on the design of a nitinol skeletal fixation device that utilizes 3D-printed porosity to match the stiffness of surrounding bone will be discussed. In the study, stiffness has been estimated from mandibular 3D CT scan data. We have 3D printed these fixation devices using Selective Laser Melting in order to validate our CAD biomechanical modeling of stiffness-matched mandibular fixation hardware.